Carburetor



IN V EN TOR.

y 1935'.- s. F. HUNT CARBURETOR Filed Nov. 14, 1951 Sea TTWHUN T Bya 5' Q g A TTORNEX Patented July 23, 1935 CARBURETOR Scott F. Hunt, South Bend, Ind., assignor to Bendix Aviation Corporation, South Bend, Ind., a, corporation of Delaware Application November 14, 1931, Serial No. 575,026

11 Claims.

This invention relates to carburetors, and more particularly to devices for preventing discharge of fuel from a carburetor when the engine is not running.

When a gasoline-driven internal combustion engine has been run for a time and is stopped, the heat from the engine travels .by radiation and conduction to the carburetor, causing vaporization of the fuel. The fuel vapors, if permitted, will escape through the main nozzle and in so doing will forcibly expel a considerable amount of liquid fuel from the nozzle, after which the fuel is brought to its former level in the nozzle by flow from the float chamber, and the process repeated. This action is sometimes referred to as percolating and is especially objectioriable in the case of down draft carburetors,

' since they are usually located relatively close to the exhaust manifold, which heats them excessively, and in the case of a downdraft carburetor the fuel discharged by the main nozzle floods the intake manifold and thus interferes with the proper functioning of the engine.

It is an object of the present invention to prevent such action by shutting the main nozzle off from communication from the float chamber when the throttle is closed, thereby preventing loss of fuel beyond that contained in the main nozzle itself. This is accomplished by a valve interposed between the float chamber and the main nozzle and actuated in accordance with the position of the throttle, so that closing the throttle closes the valve. An economizer valve is also provided which automatically closes when the engine stops.

Further objects and advantages of the invention will be apparent from the following description, taken in connection with the appended drawing, wherein Figure 1 is a view, partly in section, illustrating a carburetor embodying the invention, and Figure 2 is a diagrammatic view of the same, the parts being shown in both figures in the positions they occupy while the engine is idling.

The carburetor shown in Figure 1 is of the down draft type, although it will be apparent that the invention may be applied to other types of carburetors. In this figure, the parts are brought into a common plane for purposes of illustration, although in practice a more compact arrangement may be preferred. The carburetor comprises the usual body portion and float chamber l2, the passage of air through the carbureting chamber being controlled by a throttle l4. The throttle is actuated in the usual manner by a manually operable rod Ii connected to a lever l8 whicn is A rod connects lever at 24, and normally acceleration pump which may be of any suitable construction,

and which is shown as comprising an inverted cup-shaped member seated over a piston 32 which is urged upwardly by means of a coil spring 34.

signed, upon opening of The acceleration pump is thus dethe throttle, to force a charge of fuel through duct 36 to the carburetor.

A cylinder 38 is mounted in the float chamber and has openings 40 therein to convey fuel from the float chamber through a passage 42 to a metering plug 44 provided with a metering orifice 45 and thence through of the -main nozzle 49.

duct 46 to the bore 48 A valve needle 50 is slidably mounted in cylinder 38 and is adapted to seat in the upper end of passage 42 to control the flow of fuel therethrough. The needle 50 is provided with grooves or other depressions in its periphery so that it does not make a liquidtight fit in the cylinder 33,

and has an upwardly extending stem 52 provided with a compression spring 54 which urges the needle upwardly. The upper end of stem 52 bears against a lever 56 which is pivoted at 58 within the float chamber,

the other end of the lever being connected to the member 30, or to any other element reciprocated in accordance with throttle movements, so that opening the throttle will permit upward movement of needle 50 spring 54.

under the influence of A reciprocable economizer valve member 60 is mounted in a passageway 82 connecting the float chamber with duct 46. and is provided with an upper needle 63 and a lower needle .64. Needle 64 is normally urged upwardly against its seat by a compression spring 65 held in place by a metering plug 66 opening into duct 45.

63 is formed with longitudinal slots upper needle The for the passage of fuel and is reciprocably mounted in a cylinder 68 which projects into the float chamber. A transverse passage 61 connects passages 52 and 42.

Directly above needle 63 is a plunger 10 which is urged downwardly by a spring 12 and is connected at its upper end to a piston 14 movable in a cylindrical bore 18 which communicates, by way of a duct 80, with the carbureting chamber posterior to the throttle, the suction transmitted through duct to the upper face of piston 14 e, at closed or partially 55 causing the piston to ris open throttle, against the resistance of spring 12, and permitting spring 65 to force needle 64 against its seat.

When the engine is stopped the economizer valve member 60 is forced downwardly until needle 63 seats and'closes the passage 62, because bore 18 is at atmospheric pressure which allows spring ,72 to move plungerlflinto contact with needle 63. Hence no fuel can fiow to the main nozzle because the closing of throttle l4 has also actuated lever 22, rod 28, lever 56 and stem 52 to seat needle 50, thereby preventing loss of fuel while the motor is standing.

When the engine is being started, valve member 60 is in its lower position and needle 50 is in its raised position (assuming that the throttle is partly opened), so that fuel flows from passage 42 through duct 67 and also through plug 44 to duct 46 to the main nozzle 49, thus giving maximum fuel feed, since the fuel flows through both metering orifices 45 and 66. When the engine is idling, needles 50 and 64 are seated, and fuel flows through needle 63, passages 61 and 42, metering orifices 45 and duct 46 to the main nozzle. At moderate engine speeds both of needles 5i! and 63 are raised, so that fuel from both flows through passage 61 and metering orifice 45 to duct 46, giving a relatively lean mixture. At open throttle, the position of the parts and the resulting flow of fuel is the same as during the starting operation.

Although a specific embodiment of the invention has been described, it is not my intention to limit the invention thereto, or otherwise, ex-

cept in accordance with the following claims.

I claim:

1. In a' carburetor having a discharge nozzle and a fuel reservoir, parallel passages leading from the reservoir to the nozzle, a connecting conduit between the passages, manually operated means controlling one passage, and suction responsive means controlling the other passage at both sides of its point of connection to the connecting conduit.

2. In a carburetor for an internal combustion engine, a throttle, a discharge nozzle, a fuel reservoir, two parallel passages leading from the reservoir to the nozzle, means operative when the throttle is closed to completely close one of said passages, and means operative when the engine is at rest to close the other of said passages.

3. In a carburetor for an internal combustion engine, a throttle, a fuel nozzle, a fuel reservoir, parallel restricted passages connecting said reservoir to said nozzle, a connecting conduit between said passages anterior to the restrictions therein, and means opening both passages when the engine is running at open throttle and closing both passages when the engine is at rest.

4. In a carburetor for an internal combustion engine, a throttle, a fuel nozzle, a fuel reservoir, parallel restricted passages connecting said reservoir to said nozzle, and means responsive to carburetor conditions for opening one passage when the engine is running at fully or partially closed throttle, opening both passages when the engine is running at fully opened throttle, and closing both passages when the engine is at rest.

5. A device as defined in claim 4, wherein said means also opens both passages when the engine is being cranked for starting with the throttle partially or wholly opened.

6. In a carburetor having a fuel discharge nozzle and a fuel reservoir, parallel passages leading from the reservoir to the nozzle, a connecting conduit between the passages, and valve means responsive to carburetor conditions for selectively obstructing the inlet opening of one passage and obstructing the other passage alternately at each side of its point of connection to the connecting conduit.

7. In a carburetor having a fuel discharge nozzle and a fuel reservoir, parallel passages leading from the reservoir to the nozzle, a connecting conduit between the passages, and valve means responsive to carburetor conditions for selectively obstructing the inlet openings of one or both of said passages and for obstructing one of said passages beyond its point of connection to the connecting conduit.

8. In a carburetor having a throttle, a discharge nozzle, and a fuel reservoir; parallel passages leading from the reservoir to the nozzle, means operated in accordance with throttle posisition to completely close one passage when the throttle is closed, and suction operated means controlling the other passage and operative to close the same when the carburetor is not operating.

9. In a carburetor having a throttle, a discharge nozzle, and a fuel reservoir; parallel passages leading from the reservoir to the nozzle, a bypass leading from one passage to the other, means operated in accordance with throttle position controlling one passage, and suction operated means controlling the other passage, both said means operating to completely close both passages when the carburetor is inoperative.

10. In an internal combustion engine carburetor having a throttle, a fuel discharge nozzle and a fuel reservoir, two parallel passages leading from the reservoir to the nozzle each provided with a metering restriction, a valve in each of said passages, and control means for said valves responsive to carburetor conditions and operative at open throttle to open both valves, to open one valve and close the other at idle and at partly open throttle, and to close both valves when the engine is at rest.

11. In an internal combustion engine carburetor having a throttle, a carbureting passage, 8. fuel reservoir, two passages leading from the reservoir to the carbureting passage, a valve in each of said passages, and control means for said valves responsive to carburetor conditions for opening both valves to permit flow of fuel from the reservoir to the carbureting passage at maximum rate during cranking and when the engine is running with the throttle opened beyond a predetermined degree, opening one valve and closing the other to permit flow of fuel from the reservoir to the carbureting passage at a lower rate when the engine is running with the throttle opened less than the predetermined degree, and closing both valves to prevent flow of fuel from the reservoir to the carbureting passage when the engine is at rest.

SCO'IT F. HUNT. 

